With just two weeks left in the campaign, President Obama and Mitt Romney are airing a final wave of TV ads in the nine battleground states expected to decide the November election. And nowhere is the fight more intense than in Ohio, the only state to have sided with the winner in all of the last 12 presidential elections. Ohio "is the embodiment of Middle America," says Albert Hunt at Bloomberg News, "and swings back and forth from Republican red to Democratic blue. Right now it looks bluish purple." Obama held a comfortable lead until early October, when his GOP challenger surged in popularity after winning the first of three presidential debates. According to the latest poll, released by Public Policy Polling on Saturday, Obama's lead has dwindled to a single percentage point. How did Romney catch up? Here, four theories:

1. Ohioans like Romney's softer image
"A rehabilitated personal image" seems to be driving Romney's gains in the Buckeye State, says Tom Kludt at Talking Points Memo. The former Massachusetts governor was unpopular in Ohio for much of the campaign, thanks to "relentless scrutiny" of his professional past and his opposition to an auto bailout that saved thousands of Ohio jobs. Romney launched a push to soften his personal and political image, however, starting with his nominating convention, and now 49 percent of the state's voters have a favorable opinion of him, while 47 percent maintain a negative one.

2. Obama's endorsements aren't as strong as in 2008
As it did four years ago, Ohio's biggest newspaper, the Cleveland Plain Dealer, is backing Obama, say Gregory Wallace and Steve Brusk at CNN, but it issued its endorsement with "far less enthusiasm than in 2008." The paper said Obama had led "the nation back from the brink of depression" but lacked "vision for the many challenges" still ahead. The editorial board said it was "sorely tempted" to throw its support behind Romney, "a man of public achievement and private honor," but couldn't be sure "which Romney" we'd get, the staunch conservative of the primaries or the "reborn moderate of recent weeks." Meanwhile, another of Ohio's most influential papers, The Columbus Dispatch, strongly urged voters to back Romney.

3. Obama's attack ads are turning off independents
Obama's latest anti-Romney ad in Ohio tells voters that the GOP candidate's opposition to the auto bailout shows he's "not one of us," says Allahpundit at Hot Air. He's distorting Romney's views — Mitt actually said that Detroit needed to go through bankruptcy court so it could shed costs and come out stronger, which it did — to caricature Romney as "sort of Gekko/Scrooge hybrid who hates working people." This portrayal of the race as a fight between "'us' and those heartless 1-percent bastards" is a total betrayal of "the Hopenchange brand circa 2008." Meanwhile, Romney is running ads calling for bipartisanship, says Rick Moran at The American Thinker. That's why independents and moderates are joining his camp.

4. The polls are exaggerating Romney's gains
The polls showing Romney gaining steam in Ohio exclude people who only use cell phones, says Nate Cohn at The New Republic. Cell-phone-only voters aren't "just younger and non-white," they lean Democratic, so any poll that overlooks them tilts naturally toward Romney. Surveys taken after the first debate that included these voters showed that Obama was still up by three or four percentage points in the state, despite Romney's post-debate bump. Since then, however, only polls most favorable to Romney have revisited Ohio. Three polls that gave Obama his biggest lead — of nine, 10, and 11 percentage points — haven't taken fresh surveys since the early October debate. "The bottom line: Ohio is close, but Obama's lead remains clear with 16 days to go."

Read more political coverage at The Week's 2012 Election Center.